The heart is a hollow muscular organ of a somewhat conical form; it lies between the lungs in the middle mediastinum and is enclosed in the pericardium. The heart rests obliquely in the chest behind the body of the sternum and adjoining parts of the rib cartilages, and typically projects farther into the left than into the right half of the thoracic cavity so that about one-third is situated on the right and two-thirds on the left of the median plane. The heart is subdivided by septa into right and left halves, and a constriction subdivides each half of the organ into two cavities, the upper cavity being called the atrium, the lower the ventricle. The heart therefore consists of four chambers; the right and left atria, and right and left ventricles, with one-way flow valves between respective atria and ventricles and at the outlet from the ventricles.
Heart valve replacement may be indicated when there is a narrowing of a native heart valve, commonly referred to as stenosis, or when the native valve leaks or regurgitates, such as when the leaflets are calcified. When replacing the valve, the native valve may be excised and replaced with either a biologic or a mechanical valve.
Conventional heart valve surgery is an open-heart procedure conducted under general anesthesia, and is a highly invasive operation. The first 2-3 days following surgery are spent in an intensive care unit where heart functions can be closely monitored. The average hospital stay is between 1 to 2 weeks, with several more weeks to months required for complete recovery.
In recent years, advancements in minimally-invasive surgery and interventional cardiology have encouraged some investigators to pursue percutaneous replacement of the aortic heart valve. Percutaneous Valve Technologies (“PVT”), formerly of Fort Lee, N.J. and now part of Edwards Lifesciences of Irvine, Calif., has developed a plastically- or balloon-expandable stent integrated with a bioprosthetic valve. The stent/valve device, now called the Edwards Sapien™ Heart Valve, is deployed across the native diseased valve to permanently hold the valve open, thereby alleviating a need to excise the native valve. The Edwards Sapien™ Heart Valve is designed for delivery with the RetroFlex™ delivery system in a cardiac catheterization laboratory under local anesthesia using fluoroscopic guidance, thereby avoiding general anesthesia and open-heart surgery.
Some researchers propose implanting prosthetic heart valves at the aortic annulus using a direct-access transapical (through the left ventricular apex) approach (e.g., U.S. Patent Publication No. 2006-0074484). The left ventricular apex LVA is directed downward, forward, and to the left (from the perspective of the patient). The apex typically lies behind the fifth left intercostal space (or between the fourth and fifth), 8 to 9 cm from the mid-sternal line, and about 4 cm below and 2 mm to the medial side of the left mammary papilla. Access to the left ventricle may therefore be attained through an intercostal incision positioned over the fifth left intercostal space. Such an approach is often termed a “mini-thoracotomy,” and lends itself to surgical operations on the heart carried out using one or more short tubes or “ports”—thus, the operations are often referred to as “port-access” procedures.
Dehdashtian in U.S. Patent Publication No. 2007-0112422 discloses a port-access delivery system for transapical delivery of a prosthetic heart valve including a balloon catheter having a steering mechanism thereon that passes through an access device such as an introducer. The surgeon forms a puncture in the apex with a needle, advances a guidewire, then a dilator, and finally the introducer. Purse string sutures are pre-installed around the puncture to seal against blood leakage around the various devices and provide a closure after the procedure. During the procedure the doctor/assistant is able to apply tension to the purse-string-suture, which prevents inadvertent blood loss. After the deployment of the heart valve, the purse sting-suture is then used to permanently close the opening of the heart by drawing concentric tension on the suture ends, and tying a secure knot. The aforementioned Edwards Sapien™ Heart Valve may be inserted transapically with the Ascendra™ delivery system, much like the system disclosed in Dehdashtian.
Purse string sutures are often affixed to the heart, major arteries, and/or major veins to permit secure placement of tubes for cardiopulmonary bypass (CPB), for instance. Specifically, purse string sutures are used to seal the tissue around a cannula placed within the cardiac tissue. A purse string suture usually consists of a synthetic filament placed in a circular pattern, which is secured by taking four to five bites of tissue placed at uniform intervals around a tube, for example, from positions (with respect to a 12-hour clock face) at 1:00 to 2:00, 4:00 to 5:00, 7:00 to 8:00, and 10:00 to 11:00. Two concentric sutures usually are employed in the event that one suture breaks, and to help minimize bleeding around the surgically inserted tube. If blood pressure is not excessively high, a single purse string suture can be employed. When the tube is removed at the end of the procedure, the two ends of each suture filament are tied together to produce a water-tight seal.
Installation of the purse string sutures may be somewhat time-consuming. Also, this procedure is often performed on elderly patients, where the tissue of the heart is friable and may hold sutures poorly. Consequently, when the doctor/assistant applies tension to the purse string-suture there may be a possibility that the tissue will tear.
Despite known techniques for sealing tissue punctures in port-access procedures, improved methods and apparatuses that are more robust and even less invasive are needed.